Immobilization of xylan-degrading enzymes from Scytalidium thermophilum on Eudragit L-100

Xylanase from Scytalidium thermophilum was immobilized on Eudragit L-100, a pH sensitive copolymer of methacrylic acid and methyl methacrylate. The enzyme was non-covalently immobilized and the system expressed 70% xylanase activity. The immobilized preparation had broader optimum temperature of activity between 55 and 65 degrees C as compared to 65 degrees C in case of free enzyme and broader optimum pH between 6.0 and 7.0 as compared to 6.5 in case of free enzyme. Immobilization increased the t(1/2) of enzyme at 60 degrees C from 15 to 30 min with a stabilization factor of 2. The K-m and V-max values for the immobilized and free xylanase were 0.5% xylan and 0.89 mu mol/ml/min and 0.35% xylan and 1.01 mu mol/ml/min respectively. An Arrhenius plot showed an increased value of activation energy for immobilized xylanase (227 kcal/mol) as compared to free xylanase (210 kcal/mol) confirming the higher temperature stability of the free enzyme. Enzymatic saccharification of xylan was also improved by xylanase immobilization.